In 2006, West Fertilizer had a complaint filed against it for a lingering smell of ammonia, the Texas Commission on Environmental Quality website shows.

Separately, the plant had informed the Environmental Protection Agency that it presented no risk of fire or explosion, according to The Dallas Morning News. It did so in an emergency planning report required of facilities that use toxic or hazardous chemicals.

The plant's report to the EPA said even a worst-case scenario wouldn't be that dire: There would be a 10-minute release of ammonia gas that wouldn't kill or injure anyone, the newspaper reported.

We do not know for sure yet but it is a plausible hypothesis to check into. 'Things happen' but there are also engineering that make them likely to happen, especially in cases where there have been bad omens left unaddressed, silenced, or covered up.